Identification of the Optimal Analgesic Dose of Intrathecal Hydromorphone for Pediatric Patients Undergoing Posterior Spine Surgery for Idiopathic Scoliosis

This study is a sequential coin based up-down dose allocation method with the goal of identifying the ED90 for intrathecal hydromorphone (ITH) in idiopathic adolescent scoliosis repair via the posterior approach. A starting dose of 3.5 mcg/kg of hydromorphone was determined by current practice at the institution as well as upon review of available literature of previously used ITM doses in pediatric spine patients. Subsequent participants will receive higher (step "up") or lower (step "down") from this starting dose. Steps "down" from the starting dose will be smaller than steps "up" to ensure maintenance of adequate analgesia and to allow more accurate estimate of the optimal dose should it decrease beyond our starting dose. Steps "up" from the starting dose were chosen based on commonly used weight-based doses in our current practice. A maximum dose of 400 mcg, despite patient weight, was determined based on expert consensus and review preparatory to research query. Each patient was assigned to a weight-based dose arm, between 3.5mcg/kg-7.0mcg/kg or up to a maximum of 400 mcg. The anesthesiologist covering the case (high lumbar or thoracic corrections) or the surgeon (low lumbar corrections) will administer the medication at the low lumbar level.

ITH dose adjustments for subsequent study patients will be based on the efficacy of the dose used with the prior patient. Efficacious ITH administration will be defined as all NRS scores ≤5 within the first 18 hours after administration (binary outcome). If the NRS score was >5 within 18 hours or if the patient required supplemental opioid administration for pain control (suggestive of insufficient analgesia), the dose will be increased for the next enrolled study patient. If the pain score remains ≤5 within 18 hours of opioid administration, the next patient will receive the next lower dose or the same dose as the previous patient. Patients excluded after randomization will be removed from the study.